U.S. patent application number 11/916729 was filed with the patent office on 2008-12-18 for method and device for production of nanofibres from the polymeric solution through electrostatic spinning.
This patent application is currently assigned to El-Marco, s.r.o. Invention is credited to Ladislav Mares, David Petras, Denisa Stranska.
Application Number | 20080307766 11/916729 |
Document ID | / |
Family ID | 36933472 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080307766 |
Kind Code |
A1 |
Petras; David ; et
al. |
December 18, 2008 |
Method and Device for Production of Nanofibres From the Polymeric
Solution Through Electrostatic Spinning
Abstract
Production method of nanofibres from the polymeric solution
through electrostatic spinning in electric field created by a
difference of potentials between the collecting electrode (4) and
pivoted spinning electrode (1) of an oblong shape touching by a
part of its circuit the polymeric solution (3), while by rotation
of the spinning electrode (1) the polymeric solution (3), at least
by a portion of its surface, is carried out into the electric field
in which on the surface of the collecting electrode (4) the
nanofibres are created which are carried to the collecting
electrode (4) and deposited on the surface of a basic material (5)
guided between the spinning electrode (1) and the collecting
electrode (4) in vicinity of the collecting electrode (4). The
polymeric solution (3), on surface of the spinning electrode (1) in
a place of intersection of surface of the spinning electrode (1)
with the plane interlaid by the axis of the spinning electrode (1)
and being perpendicular to the plane of the base material (5),
along the whole length of the spinning electrode (1), is subject to
the electric field of a maximum and equal intensity, through which
a high and even spinning effect is achieved along the whole length
of the spinning electrode (1). The invention also relates to the
device for production of nanofibres from polymeric solution through
electrostatic spinning.
Inventors: |
Petras; David; (Peroltice,
CZ) ; Mares; Ladislav; (Liberec, CZ) ;
Stranska; Denisa; (KJojetin, CZ) |
Correspondence
Address: |
DORITY & MANNING, P.A.
POST OFFICE BOX 1449
GREENVILLE
SC
29602-1449
US
|
Assignee: |
El-Marco, s.r.o
:oberec
CZ
|
Family ID: |
36933472 |
Appl. No.: |
11/916729 |
Filed: |
June 1, 2006 |
PCT Filed: |
June 1, 2006 |
PCT NO: |
PCT/CZ2006/000037 |
371 Date: |
September 2, 2008 |
Current U.S.
Class: |
57/402 |
Current CPC
Class: |
D01D 5/0069
20130101 |
Class at
Publication: |
57/402 |
International
Class: |
D01D 5/00 20060101
D01D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2005 |
CZ |
PV 20005-360 |
Claims
1. Production method of nanofibres from the polymeric solution (3)
through electrostatic spinning in electric field created by a
difference of potentials between the collecting electrode (4) and
pivoted spinning electrode (1) of an oblong shape toughing by a
part of its circuit the polymeric solution (3), while by rotation
of the spinning electrode (1) the polymeric solution (3), at least
by a portion of its surface, is carried out into the electric field
in which on the surface of the collecting electrode (4) the
nanofibres are created which are carried to the collecting
electrode (3) and deposited on the surface of a basic material (5)
guided between the spinning electrode (1) and the collecting
electrode (3) in vicinity of the collecting electrode (3),
characterized by that the polymeric solution (3) on surface of the
spinning electrode (1) in a place of intersection of surface of the
spinning electrode (1) with the plane interlaid by the axis of the
spinning electrode (1) and being perpendicular to the plane of the
base material (5), along the whole length of the spinning electrode
(1) is subject to the electric field of a maximum and equal
intensity, through which a high and even spinning effect is
achieved along the whole length of the spinning electrode (1).
2-22. (canceled)
Description
TECHNICAL FIELD
[0001] The invention relates to the production method of nanofibres
from the polymeric solution through electrostatic spinning in
electric field created by a difference of potentials between the
collecting electrode and pivoted spinning electrode of an oblong
shape touching by a part of its circuit the polymeric solution,
while by rotation of the spinning electrode the polymeric solution,
at least by a portion of its surface, is carried out into the
electric field in which on the surface of the collecting electrode
the nanofibres are created which are carried to the collecting
electrode and deposited on the surface of a basic material guided
between the spinning electrode and collecting electrode in vicinity
of the collecting electrode.
[0002] The invention also relates to the device for production of
nanofibres from polymeric solution through electrostatic spinning
in electric field created by a difference of potentials between the
collecting electrode and the pivoted spinning electrode of an
oblong shape coupled with a drive and touching by at least a
portion of its surface the polymeric solution with the objective to
carry out the polymeric solution by these portions of surface into
the electric field between the spinning electrode and the
collecting electrode, while between the spinning electrode and the
collecting electrode the track for passage of the basic material is
created, the surface of which from the side of the spinning
electrode serves for depositing of the nanofibres created.
BACKGROUND ART
[0003] The nanofibres are prepared from a broad range of polymers
and polymer compounds, this either from the solutions using the
solvents on the water or non-water basis. Various low-molecular
additives may or need not to be added into the solutions as the
need may be, which after then regulate some important physical
properties of the solution being subject to spinning or which bring
new chemical, physical, biological or other properties into the
resultant polymer. At the same time the nanonfibres may be prepared
also from the melts of polymers, but in contrast to the in
principle similar processes of creating the polymeric melts, during
processing of solutions smaller diameters of fibres are reached
thanks to lower viscosity of solutions when compared with melts.
For formation of solutions the mechanical forces of flowing gaseous
media or the coulomb forces in electrostatic field are being used,
so called electrostatic spinning, which leads to the fibres of
smaller diameters.
[0004] The patents U.S. Pat. No. 6,382,526 and U.S. Pat. No.
6,520,425 represent an example of preparation of nanofibres from
polymeric solution through a stream of air. The diameters of
nanofibres produced by this technology are of 200 to 3000
nanometers.
[0005] The patent applications WO 0127365, WO 0250346, US
2002/0175449 A1, US 2002/084178 A1 and WO 2005/024101 A1 describe
examples of preparation of nanofibres from polymeric solutions upon
acting of electrostatic field of an average intensity of 50.000 to
500.000 V/m. The first four mentioned applications represent a
solution which partially resembles the solution quoted in patents
using the mechanical forces of gas stream. Again here are the jets
of circular section and of inner diameter 0.5 to 1.5 mm), to which
the voltage of direct current is applied. Opposite the jet from
which the polymeric solution is forced out, mostly the grounded
electrode (collecting electrode) is positioned. Such arrangement
results in drawing of a thin further splitting beam of polymeric
solution which finally provides the nanofibres. The greatest
problem of this method is a low output. On one spinning jet, 0.1 to
1 gram of polymer in one hour may be, which, from the point of view
of industrial usage, creates the production of nanofibres according
to these solutions rather problematic. To the benefit of an output
and also of homogeneity of the applied layer to the collecting
electrode or to the ground, which is positioned between the jet and
the collecting electrode in its vicinity, a group of static or
moving jets can be built. Unfortunately the number of jets cannot
be increased in an unlimited way, as well as there are limits as to
the distance of jets among each other, which is given by the
electric field itself, so also this solution does not bring a
decisive point as regards an output. Next to this, here are further
limits arising out of the general physical laws as the
impossibility to increase the tension above the limit of a specific
dielectric strength of air in the space of spinning,
unsubstantiality of the proportional increasing of distance of
electrodes, etc.
[0006] The GB 1 346 231 publishes a device for electrostatic
spinning of polymer solutions containing the annular spinning
electrode pivoted in a vertical plane by its lower part in
polymeric solution and by its upper part between two vertically
mounted collecting electrodes. The solution being subject to the
spinning is carried out by the surface of a ring of the spinning
electrode, at the same time the spinning process proceeds in the
upper part of the annular spinning electrode positioned between the
collecting electrodes in places, which are as much close as
possible to these flat electrodes. The device can only hardly be
used in industry as it is complicated, non-productive and the
possible layer of fibres, eventually the non-woven textile produced
by electrostatic spinning would be of a very irregular thickness
and structure.
[0007] Next to this, the solution according to EP 1059106 A2 is
known, which describes a device for change over of the solution or
the polymer melt into the fibrous structure that contains a plane
collecting electrode and a spinning electrode between which the
electric field is created. The spinning electrode serves for
transportation of the solution or of polymer melt (hereinafter
referred to as solution only) into the electric field,
simultaneously it is essential, that layers of polymer solution of
a sufficiently high curvature are created on it on which the charge
of electric field is concentrated so that the nanofibres are
created from solution layer or from the melt. The nanofibres
created are carried to the collecting electrode by action of the
Coulomb forces. In one of the described variants, the spinning
electrode is formed by a pivoted disc provided on its perimeter by
protrusions, and the disc is dipped by a part of its perimeter into
the polymer solution and brings the liquid polymer out into the
electric field. The disc surface is wettable by a polymer solution
so that this creates a coating on it. Once the disc rotates, each
protrusion is gradually covered by a layer polymer solution, which
gradually gains a charge of electrode, this means negative) and
thanks to a high curvature the nanofibres are created on it.
Polymer solution which has not been consumed returns back to the
reservoir. The disc is positioned with the rotation axis parallel
to the movement direction of the base fabric. The disadvantage of
this solution is a small efficiency, because into the electrostatic
field only a small quantity of polymer solution being subject to
spinning penetrates and only a small portion is changed over into
the fabrics. Another disadvantage is irregular thickness of
nanofibre layers along the width.
[0008] Further there is depicted an askew mounting of a larger
quantity of discs provided with protrusions on their perimeter,
which may be positioned in a skew position towards the discharging
electrode. According to the invention it is advantageous if the
disc cores are of an isolation material to prevent effects
superimposing the electric field. The solution should bring an
advantage in a more even coating of fibre layer to the base
material. The solution is very complicated due to the rotational
drive of askew positioned discs and increasing of evenness of
applied layer of nanofibres is possible only in the direction of
movement of the base material and it cannot be presumed even in the
direction of the width of the base material.
[0009] Other execution describes the discs illustrated in FIG. 14,
on the perimeter of which the shaped protrusions are created and
under those a collecting cavities for polymeric solution to
facilitate dosing of quantity of polymeric solution and its
advantage should consist in that the same quantity of polymeric
solution is always repeatedly brought into the electrostatic field
for spinning. The disadvantage of this solution is that the
spinning takes place on the peaks of protrusions where
concentration of the charge is the greatest while the collecting
cavities are arranged on the smaller diameter than the peaks of
protrusions, so it is complicated to transport the measured off
quantity of a polymeric solution to the respective peak. Moreover
upon rotation direction of a disc in the arrow direction
illustrated in FIG. 14 by an arrow into the collecting cavities
(151) no polymeric solution is taken, it would only be possible
that the solution flows down into them which got stuck on surface
of the protrusions at their rotation in the upwards direction. At
the same time it is improbable, that always the same quantity of
polymeric solution is dosed into the collecting cavities.
[0010] The technology shown in the WO 2005/024101 A1 patent tries
to successfully solve the problem with output and other issues of
the above mentioned solutions. In this case the spinning electrode
is created of an electrode in the shape of a cylinder which rotates
around its main axis and with its lower part of the surface is
being dipped into the polymeric solution. The cylinder axis is
positioned in the plane being parallel with a plane of a base
material and perpendicular to the motion direction of the base
material. On a surface of the cylinder a thin layer is being
carried out from which at the simultaneous creation of so called
Taylor cones the above mentioned beams of solution are being drawn
which after then form on a collecting counter-electrode or on a
suitable base layer, a layer of nanofibres in front of it. The
mentioned technology works very good for polymeric solutions on a
water basis. It does not solve the spinning issue for solutions on
a non-water basis. This is connected with a basically different
character of water and non-water solutions, which is first of all
given by the presence of a strong dipole moment in a small water
molecule. This predetermines totally different properties of water
and non-water polymeric solutions from the point of view of effects
of the outer electric field. Also at the water polymeric solutions
the created layer of nanofibres is not totally even along the whole
length of the spinning electrode.
[0011] From the above mentioned it is obvious that the principle of
the up to now designed devices for preparation of quality
nanofibres and layers of nanofibres is always a couple of
electrodes on a different electrical potential. Without
exaggeration the electrodes and their structure are the heart of
the whole device and they predetermine by a decisive manner the
success or failure of the whole device in production of
nanofibres.
[0012] The objective of the invention is to create a method and a
device which could be industrially usable also for spinning of
polymeric solutions in solvents on the non-water basis and which
would achieve a high spinning output and at the water and non-water
solutions of polymers would further increase the evenness of
created layer of nanofibres.
THE PRINCIPLE OF THE INVENTION
[0013] The objective of the invention has been reached, through a
method of production of nanofibres from the polymeric solution by
electrostatic spinning in electric field according to the invention
whose principle consists in that the polymeric solution on surface
of the spinning electrode in a place of intersection of surface of
the spinning electrode with the plane interlaid by the axis of the
spinning electrode and being perpendicular to the plane of the base
material, along the whole length of the spinning electrode is
subject to the electric field of a maximum and equal intensity,
through which an equal and even spinning effect is achieved along
the whole length of the spinning electrode, and as a result of it
also the even thickness of nanofibre layer deposited on a base
material.
[0014] It is advantageous, if the polymeric solution is brought
into the electric field in quantities of same batches divided one
from another that are moving around the circular tracks in the
electric field while the mutual position of batches does not change
and the batches are arranged in groups of batches, situated along
the length of the spinning electrode in a plane running through the
axis of the spinning electrode and perpendicular to the plane of
base material with respect to the collecting electrode on the
equipotent line of the highest intensity of electrical field
between the spinning electrode and collecting electrode.
Distribution of the polymeric solution into batches and positioning
of each batch in the time when it is as close as possible to the
collecting electrode in a place with highest intensity of electric
filed.
[0015] The direction of carrying out the polymeric solution batches
divided one from another is, with advantage, reverse towards the
sense of base material movement through which the greater evenness
of created nanofibre layer is achieved.
[0016] The principle of a device for production of nanofibres from
polymeric solution through electrostatic spinning in electrical
field consists in that the coating surface of sections of surface
of the spinning electrode serving for carrying out the polymeric
solution into the electric field is, in the plane running through
the axis of the spinning electrode and perpendicular to the plane
of the base material, of a shape created by the equipotent line of
electric field between the spinning electrode and collecting
electrode being of the highest intensity.
[0017] For spinning of the water polymeric solutions it is
sufficient, if the coating surface is filled, which makes the
structure of these devices easier.
[0018] For spinning of the water as well as the non-water polymeric
solutions the spinning electrode contains a system of corrugated
lamellas made of a flat electrically conductive material, which are
towards the rotation axis mounted tangentially with their
corrugation, at the same time in a plane perpendicular to the plane
of the base material and running through the rotation axis of the
spinning electrode and in the centre of the corrugated lamella they
have a shape of equipotent line of the highest intensity of
electric field between the spinning electrode and collecting
electrode. Such spinning electrode is able to carry out a
sufficient quantity of polymeric solution into the most suitable
places of electric field between the spinning and collecting
electrode, and simultaneously to perform a good spinning also of
non-water polymeric solutions.
[0019] At the same time it is advantageous, especially for a
quicker starting of spinning and maintaining a constant spinning
process, if the lamellas are provided with protrusions on their
outer side.
[0020] The spinning electrode contains a system of lamellas
arranged radial and longitudinally around the rotation axis of the
spinning electrode evenly around its perimeter and provided with
tips protruding outwards, while in the position when the tips of
the spinning electrode are in the plane perpendicular to the plane
of the base material, the peaks of these tips are laying on the
equipotent line of the highest intensity of electric field between
the spinning and collecting electrode.
[0021] According to the claim 9 the lamellas are made of a thin
electrically conductive material together with the tips and their
peaks. This execution is a simple one and does not increase too
much the price of the spinning electrode.
[0022] At the same time it is advantageous for starting the
spinning process if the tip peaks are bow or tip shaped.
[0023] According to the claim 12 the lamellas are made of a flat
electrically conductive material and in the outward direction are
equipped with tips of a cuboid shape finished with formed
peaks.
[0024] According to the claim 13 these tips are cylindrical and
they are finished with formed peaks.
[0025] According to the claim 14 the formed peaks are made of a
bevelled surface oriented in the rotation direction of the spinning
electrode.
[0026] According to another execution the formed peaks are made of
bevelled surface oriented in the rotation direction of the spinning
electrode, while in the bevelled surface there is created a recess
serving for measuring of always same quantity of the taken
polymeric solution and for exposure of a batch of polymeric
solution to action of electric field between the spinning and
collecting electrode.
[0027] According to the claim 16 the formed peaks are created by a
little seat which with advantage contains the upper deflected
surface oriented in the direction of lamella length and towards the
rotation direction of the spinning electrode oriented front
deflected surface and the rear deflected surface and it enables an
ideal exposure of the polymeric solution batch being on the little
seat to action of electric field which acts evenly to the batch
from all sides.
[0028] To reach greater widths of produced layer of nanofibres, at
least two side by side laying spinning electrodes are arranged on
one axis. [0029] To reach a greater thickness of the produced layer
of nanofibres, the spinning electrodes are arranged at least two
one after another towards the movement direction of the base
material. [0030] To reach a great widths of produced layer of
nanofibres, the spinning electrodes are arranged at least two side
by side on one axis and at least in two rows one after another,
while the spinning electrodes of the following row are situated in
place of gaps between the spinning electrodes of the previous row.
[0031] At the same time the rows of the spinning electrodes are
positioned perpendicular to the movement direction of the base
material, or [0032] they are positioned askew to the movement
direction of the base material.
DESCRIPTION OF THE DRAWING
[0033] Examples of the device execution as per the invention are
schematically shown in the attached drawings, where
[0034] the FIG. 1 illustrates a cross section of the device with
lamellar spinning electrode with lamellas provided with tips with
formed peaks,
[0035] the FIG. 2 shows a longitudinal section of the device with
the spinning electrode with filled coating surface,
[0036] the FIGS. 3a and 3b show a view to the lamellar spinning
electrode with flat lamellas,
[0037] the FIGS. 4a and 4b a view to the wave lamellar spinning
electrode,
[0038] the FIG. 5a a view to the lamellar spinning electrode with
lamellas equipped with cylindrical tips with formed peaks, 5b a
view to lamella with tips arranged in a mutual interval,
[0039] the FIG. 6 a view to lamellar spinning electrode with
lamellas provided with tips of a cuboid shape,
[0040] the FIG. 7a a detail of formed peaks of a flat lamella of
the lamellar spinning electrode,
[0041] the FIG. 7b the peaks of tips of the lamellar spinning
electrode with a simple bevelled surface modified into a shape of
dimple,
[0042] the FIG. 7c the peaks of tips of the lamellar spinning
electrode with a simple bevelled surface modified into a shape of
dimple,
[0043] the FIG. 7d the peaks of tips of the lamellar spinning
electrode with a little seat,
[0044] the FIG. 8a a serial arrangement of the spinning
electrodes,
[0045] the FIG. 8b a parallel arrangement of the spinning
electrodes,
[0046] the FIG. 8c a serial and a parallel arrangement of spinning
electrodes in combination and with shift by a half length of the
spinning electrodes and
[0047] the FIG. 8d an arrangement according to the FIG. 8c with a
rotation axis of the spinning electrodes in a different directions
towards the shift direction of the base material.
EXAMPLES OF EMBODIMENT
[0048] A device for production of nanofibres from the polymeric
solution through electrostatic spinning illustrated in the FIG. 1,
3 to 7 contains the spinning electrode 1 created by lamellas 11
arranged radial and longitudinally around the axis 12, which is by
a known not illustrated manner pivoted in the body of the
equipment. The individual lamellas 11 of the spinning electrode 1
or the whole spinning electrode 1 are in a known not illustrated
manner connected with a not illustrated source of a high voltage or
grounded. The lamellas 11 are spread along the whole length of the
spinning electrode 1 and they are evenly distributed around its
perimeter. In the illustrated execution the axis 12 of the spinning
electrode is created by a shaft 121, which is by a known not
illustrated manner coupled with a drive ensuring its rotation
movement.
[0049] Under the spinning electrode 1 there is positioned a
reservoir 2 with polymeric solution 3. Lamellas 11 in the lower
section of the spinning electrode 1 are dipped in the polymeric
solution 3. Each lamella contains a lot of tips 111, on the ends of
which there are the formed peaks 1111 created, which are the
carrying surfaces for the drips 31 of the polymeric solution 3, as
illustrated in FIG. 1.
[0050] Above the spinning electrode 1 there is arranged the
collecting electrode 4 connected in a known not illustrated manner
to the source of high voltage of an opposite polarity than the
spinning electrode 1 or the grounded one. The axis 12 of the
spinning electrode is mounted parallel with the collecting
electrode 4, respectively with a plane of the collecting electrode
4. Between the collecting electrode 4 and the spinning electrode 1,
after applying the high voltage to at least of one from them and
after grounding of the second electrode, or connecting the second
electrode to a high voltage of an opposite polarity, an intensive
electric field is created that ensures generation of Taylor cones
on the peaks 1111 of the tips 111 of lamellas 11 and drawing of the
beam 32 of the polymeric solution 3 from peaks 1111 of the tips 111
towards the collecting electrode 4.
[0051] Between the spinning electrode 1 and the collecting
electrode 4, usually in the vicinity of the collecting electrode 4,
there is performed a guidance for the base material 5, created by
the base textile or by another suitable material according to the
requirements for usage of the produced textile containing a layer
of nanofibres or a textile created by a nanofibre layer. In the
illustrated execution the guidance contains two pairs of
rollers--the feed rollers 61 and the delivery rollers 62. The base
material may be created by an infinite band mounted on a pair of
rollers out of which at least one is driven, while the nanofibre
layer is picked up from the infinite band by a known manner and is
deposited into the package. The movement direction of the base
material 5 is usually concurrent with the rotation direction of the
spinning electrode 1. To increase the evenness of the layer applied
33 of nanofibres it is nevertheless advantageous to reverse the
direction of rotation of the spinning electrode 1 and to rotate the
spinning electrode 1 against the sense of movement of the base
material 5.
[0052] The formed peaks 1111 are created by small surfaces formed
for optimalization of the shape of drip 31 of polymeric solution 3
on the formed peak in electric field after carrying out the
polymeric solution from the reservoir by the lamella 11. Each such
drip 31 represents a batch of polymeric solution 3 brought into the
electric field for spinning.
[0053] The FIG. 2 shows an alternative of execution of a device for
production of nanofibres from water polymeric solution through
electrostatic spinning according to the invention. In this case,
when compared with the WO 2005/024101 A1, the cylindrical body
creating the spinning electrode 1 is formed in a plane running
through the axis 12 of rotation of the spinning electrode 1 and
perpendicular to the plane of the base material 5 into the shape of
equipotent line of electric field between the spinning electrode 1
and the collecting electrode 3 of the highest intensity for the
selected potential of electric field. The coating surface of the
spinning electrode 1 is filled and is not created by lamellas
arranged along the length of the spinning electrode 1, as it is at
the above described executions. At the execution of the spinning
electrode 1 according to the FIG. 2 it is possible to shape the
outer surface e.g. by means of the radial protrusions in the form
of collars or tips, protrusions in the shape of spiral or axial
protrusions like at the WO 2005/024101 A1.
[0054] In other alternative execution which is not illustrated, for
production of nanofibres especially of water polymeric solutions,
the spinning electrode may be created of system of wheels arranged
coaxially side by side on a common shaft, while the coating surface
of such system lies in a plane running through an axis of the
spinning electrode and perpendicular to the plane of base material
created by the equipotent line of electric field between the
spinning and collecting electrode of the highest intensity for the
selected potential of electric field. At the same time the wheels
may be arranged closely side by side or with a certain spacing and
they may be provided with protrusions of various shapes on their
perimeter.
[0055] The execution of the spinning electrode 1 for spinning of
polymers both from non-water and water solutions is illustrated in
FIG. 3a in a general view and in FIG. 3b in detail of portion of
the electrode. The spinning electrode 1 contains the shaft 12, on
which the faces 122 are attached and in them the flat oblong
lamellas 11 are mounted in radial manner, on which are formed
outwards protruding flat tips 111 finished with formed peaks 1111,
which are shaped into the form of bow. The tips 111 of individual
lamellas 11 have a different length, while their coating curve is
an equipotent line of electric field made between the spinning
electrode 1 and the collecting electrode 4 in a plane passing
through an axis 12 of the spinning electrode and perpendicular to
the plane of base material 5.
[0056] Another example execution of the spinning electrode 1 for
spinning of polymers from water as well as non-water solutions is
shown in the FIG. 4a in a view against the electrode axis, and the
FIG. 4b shows arrangement of lamellas with respect to the shaft in
axonometric view. At this execution the lamellas 11 are created by
a corrugated flat electrically conductive material and they are
with their ends mounted in the faces 122 attached to the shaft 121,
at the same time with respect to the shaft 121 the lamellas 11 are
mounted tangentially with their corrugation. In the direction
outwards from the spinning electrode 1 a thin surface of lamella
serpentine 11 is directed, which in the radial direction in a plane
perpendicular to plane of the base material and passing through a
centre of the wavy lamella 11 is shaped into the form of equipotent
line of the highest intensity for the selected potential of
electric field created between the spinning electrode 1 and the
collecting electrode 4. In the not illustrated example of execution
the individual lamellas 11 are provided with protrusions on their
outer side.
[0057] The example of execution according to FIG. 5a shows the
spinning electrode 1 for spinning of polymers from water as well as
non water polymeric solutions 3, which contains on the shaft 121
attached faces 122, between which are in radial manner mounted the
lamellas 11 provided with outwards aiming tips 111, which are
finished with formed peaks 1111. The coating curve of the peaks
1111 of lamella tips represents an equipotent line of the highest
intensity of electric field created between the spinning electrode
1 and the collecting electrode 4 in a position, when the tips 111
of the spinning electrode are in a plane perpendicular to the plane
of the base material 5.
[0058] In execution according to the FIG. 5a the tips 111 are of a
cylindrical shape, they are arranged closely side by side a their
formed peaks 1111, illustrated in a detail view in FIG. 7c contain
a bevelled surface 1111a, in which there is a recess 1111b, which
in an advantageous case is of a ball or cone shape. The formed peak
111 of lamella of the spinning electrode is in other execution
created by a bevelled surface 1111a only as shown in the FIG. 7b,
or by a little seat 1111c, illustrated in FIG. 7d. The little seat
contains the upper deflected surface S1 oriented in the direction
of length of lamella 11 and the front deflected surface S2 oriented
with respect to the rotation direction of the spinning electrode
forwards and the rear deflected surface S3 oriented with respect to
the rotation direction of the spinning electrode backwards. In the
not illustrated execution the front and the rear surfaces of the
little seats 1111c may be created by a flat bevelled surfaces. In
another not illustrated execution in the upper deflected surface of
the little seat 1111c there may be created a recess or a
dimple.
[0059] The FIG. 5b shows an example execution of lamella of the
spinning electrode according to FIG. 5a, at which the tips 111 are
on the lamella 11 arranged with a certain spacing. The formed peaks
1111 contain the bevelled surface 1111a, in which the recess 1111b
is provided. The coating curve of the tip peaks 1111 of lamella
represents an equipotent line of electric field created between the
spinning electrode 1 and the collecting electrode 4.
[0060] The spinning electrode according to FIG. 6 contains the flat
lamellas 11 of a certain thickness which are similarly as at the
previous execution mounted on a shaft and in the direction outwards
they are provided with protrusions of a cuboid shape arranged
separately one from another and finished at their ends with formed
peaks 1111 that are created by a bevelled surface 1111a. The formed
peaks 1111 of lamellas may be created also by another, especially
by that above mentioned manner, i.e. for example by a recess 1111b
or little seats 1111c.
[0061] The spinning electrodes 1 may, for a purpose to reach a
greater width possibly a greater evenness and/or greater thickness
of the produced nanofibres layer 33, be arranged in a various
manners, as it is shown in FIG. 8a to 8d.
[0062] In the execution according to FIG. 8a there are in one axis
12 in a specified spacing one from another positioned at least two
spinning electrodes 1, in the illustrated example of execution
there are three spinning electrodes 1. The distance between the
spinning electrodes 1 has been chosen so that the layer 33 of
nanofibres is created on the base material 5 even between the
electrodes.
[0063] At the execution according to FIG. 8b there are arranged
three electrodes 1 in three rows 1210, 1220, 1230 one after another
in the direction of movement of the base material 5. This execution
has been designed to reach a greater thickness of the layer 33 and
it must contain at least two spinning electrodes 1 in two rows one
after another.
[0064] To reach a greater width of the produced layer 33 of
nanofibres and a greater evenness of the layer 33 of nanofibres the
spinning electrodes 1 are arranged at least two side by side on one
axis 12 and at least in two rows one after another, while the
spinning electrodes 1 of the second row 1220 are situated in places
of gaps between the spinning electrodes 1 of the first row
1210.
[0065] The rows 1210, 1220, 1230 and 1240 of the spinning
electrodes 1 are in execution according to FIG. 8c positioned
perpendicularly to the direction of movement of the base material
5.
[0066] The rows 1210, 1220, 1230 and 1240 of the spinning
electrodes 1 are positioned askew to the direction of movement of
the base material 5.
[0067] The polymeric solution 3 is in a form of defined drips
carried out into the electric field pole on the tip peaks 111 of
special lamellas 11, which, in arrangement radial and longitudinal
along the axis 12 of rotation, rotate on a common axis. The height
of tips 111 ensures that the peaks 1111 of these tips are when
passing the plane perpendicular to the plane of the base material 5
and running through the axis 12 of rotation of the spinning
electrode 1 in the equipotent lines of electric field.
Simultaneously a small surface on peaks of the tips 111, being
roughly around 1 mm.sup.2, ensures a local increase of electric
field in the place of drips, which provides optimum conditions for
starting the spinning process. The peaks 1111 of the tips 111 after
then may have various finishes, which more or less optimise the
shape of the drips. In the most simple arrangement it may be a
level surface 1111a or a recess 1111b, and in more complex variant
e.g. a little seat 1111c, the usage of which is very advantageous.
The little seat 1111c ensures that the drip will be exposed to
electrical field in a symmetric manner and simultaneously the
stored polymeric solution 3 will better wash the peaks from
remnants of polymeric solution 3, which has already passed the
process.
[0068] As mentioned above, to start the process of spinning it is
necessary that the polymeric solution 3 (optimally a small portion
of its volume) gets into an intensive electrical field. Through
experiments it has been proven that the water polymeric solutions 3
differ in principle from the non-water polymeric solutions 3 in the
meaning of spinning using the electrostatic forces. The result is
not as much surprising, because the water molecule through its
small dimension and the strong dipole moment is in an outstanding
position towards all other common solvents which have the molecules
larger and with lower or nearly no dipole moment. The values of
static relative dielectric constant .epsilon..sub.r, when water has
81, acetone 21.4, ethanol 25.1 etc., give also evidence of the
totally different character of water. Solvent represents in
solutions the main mass (commonly around 80% of wt.) and it defines
basically the properties of a polymeric solution. The polymeric
solution which is created mostly or totally by molecules non-polar
will assume a different attitude towards the external electric
field than the polymeric solution containing a quantity of polar
molecules. It is known that the dipole similarly to the magnetic
needle in magnetic field assumes towards the external electric
field a clear attitude, namely so that the vector of dipole is
parallel with vector of electric field. The molecules, at which the
chaotic movement prevailed before, are enforced to a more
consistent internal arrangement within the solution. Hence, the
water polymeric solutions are capable of internal layering to
polarised layers, which finally causes that there is an intensive
electric field as well as the whole surface of the liquid. The
polymeric solutions from nearly non-polar or non-polar solvents are
practically immune towards the external electric field, and the
field does not affect an internal re-arrangement of molecules. On
surface of such polymeric solutions the strong electric field is
not created, on the contrary the original field is weakened and the
rate of weakening is then given by the dimensions of the liquid
body (large surface and thickness considerably weaken the intensity
of electric field), which after then plays a role of simple
insulator. Thus, it is necessary to ensure the field of a high
intensity through another way, for the purpose of which the above
mentioned structure of the spinning electrode 1 serves. The peaks
1111 of lamella tips in the form of small spots (cca 1-4 mm.sup.2)
ensure for the drip, which gets stuck on them that it gets into the
electric field of a such intensity, which is especially in places
of contact of the drip with edge of lamella tip 111 (so called
triple point--contact spot of three dielectric different media),
and consequently it initiates creation of Taylor cones, drawing of
the beam of polymeric solution 3 against the collecting electrode
4. The Taylor cones are a general effect, they are a result of
forces to which the polymeric solution is subjected to and their
creation occurs once the external force (here the coulomb one)
whose vector is perpendicular to the tangential plane to the liquid
surface in place of action; it begins to prevail over the forces
developed by the inner consistency of liquid molecules and forces
of surface tension.
[0069] Practically all solutions of polymers in non-water solvents
belong to the polymeric solutions with a minimum chance for
internal change in environment of electric field. Necessary to say,
that the polymeric solution itself, to be able to initiate the
spinning process, must meet even further parameters, such as
solution viscosity given by the molecular mass of polymer, by its
concentration and temperature, further the suitable surface tension
given by the type of polymer and presence or non-presence of a
surface active substance and a suitable value of electric
conductivity of the solution which can be, if necessary, increased
by adding the low-molecular electrolyte.
[0070] The quantity of the polymeric solution 3 being subject to
spinning, thus the total performance may be affected by dimension
of the spinning electrode 1. Nevertheless the dimension of the
spinning electrode does not affect the performance directly
proportional, this even in such a manner that from a certain length
of the spinning electrode 3 it starts to be obviously
disadvantageous to continue in increasing the length as the
performance is then for length unit of the spinning electrode
substantially lower with simultaneous increase of unevenness. This
is given by the common physical laws accompanying the problems of
electric field. The solution arises in a form of various
combinations of a larger quantity of "smaller" spinning electrodes
1, when the individual spinning electrodes 1 are in the parallel or
serial arrangement or in combination of both and simultaneously the
main axis 12 of the spinning electrodes 1 need not to be
perpendicular to the direction of movement of the base material 5
in the continual production system. Next to this, the spinning
electrodes may be towards one another in a parallel arrangement
shifted by a half of its length, which further contributes to
evenness of the applied nanofibre layer 33. The final arrangement
is always given by a respective requirement for performance of the
machine (width and speed).
[0071] Another modification is represented by a rotation of the
spinning electrode 1 with respect to the movement of the base
material 5 during the continual process. Unevenness in the form of
diagonal differences in the applied quantity of the nanofibre layer
33 on the shifting base material 5, at certain polymeric solutions
3, may occur due to the fact that the process is being started
gradually and separately from each lamella 11. The effective
compensation is the speed and rotation direction of the spinning
electrode 1. In case of a speed it is optimum if the peripheral
speed of the rotating spinning electrode 1 is fifteen times to
twenty times greater than the speed of base material 5 movement.
Next to this, important is the sense of rotation of the spinning
electrode 1 with respect to the direction of movement of the base
material 5. The reverse--retrograde rotation of the spinning
electrode towards the movement of the base material 5 brings more
even results, while the rotation speed need not in such a multiple
exceed the speed of movement of the base material 5 as in the case
of rotation being concurrent with the movement.
[0072] Further modification which is brought by the invention is a
usage of various values of voltage on electrodes. It is
advantageous to create the potential necessary so that the voltage
of opposite polarity is applied to both electrodes (spinning and
the collecting one). The electric field is much more better
definable and controllable than in a case when the voltage was
applied only to one of the electrodes, and as a rule it was the
spinning electrode, while to the second electrode (the collecting
one) the zero potential was positioned. The zero potential,
especially on the collecting electrode, brings a number of
disadvantages arising out of the fact that in the vicinity of the
spinning area, i.e. the electrodes, another sections of the device
are installed, which are also on the zero potential and may in a
non-definable manner modify an electric field and to carry away the
carried out fibres into the undesirable places. Due to the small
currents (roughly hundreds of .mu.A), which are transferred by the
charged mass of the polymeric solution, the current circuit may be
closed even in spite of the otherwise considerable insulators, like
the plastic parts of the device, etc. This is removed by the
opposite potential on the collecting electrode, through which the
electrode is "made visible" for the material subject to spinning.
Much more definable impact of nanofibres to the base material 5
creates the final result of this change.
EXAMPLE 1
[0073] The spinning lamellar electrode according to FIG. 3 rotates
in the reservoir of polyamide solution PA 612 (conc. 20% wt., Mr
2800 g/mol) in an acid. Immersion of the lamella is such that only
spots of tips are dipped. The electrode rotates in a retrograde
manner towards the movement of the non-conducting spunbond base
textile.
APPLICABILITY
[0074] The method and the device as per the invention are
applicable for preparation of layers of nanofibres, especially from
polymers soluble in solvents on a non-water basis having the
diameter of nanofibres of 100 to 500 nanometers, nevertheless also
for spinning of polymers from water solutions. These layers may be
used for filtration as the battery separators, to create special
composites, for production of protective clothing, in medicine and
other areas.
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